The present invention relates to an image forming apparatus for forming an image wherein a photoreceptor is scanned to be exposed to light by a light beam, and to an assembling method of an exposure unit in the image forming apparatus.
In the image forming apparatus for forming an image wherein a photoreceptor is scanned to be exposed to light by a light beam, accuracy of incident position of the light beam on the photoreceptor has an influence on image quality. Therefore, an exposure unit is structured so that the light beam may enter at high accuracy.
In a color image forming apparatus for forming a color image by conducting a plurality of exposures, forming a plurality of images and thereby by superposing the plural images, in particular, it is requested to keep the position stated above accurately.
Typical one that conducts scanning exposure with a light beam is an exposure unit employing a laser, and with respect to adjustment of the position stated above in a laser exposure unit, there is disclosed in U.S. Pat. No. 2,570,176 official gazette, for example, an adjustment mechanism for adjusting a position and an angle of the exposure unit having a laser light source and a scanning exposure optical system in X, Y and Z directions. This adjustment mechanism adjusts at two points representing both ends of each side of the square exposure unit for each of X, Y and Z directions, and thereby adjusts the incident position of the light beam on the photoreceptor.
Each of many color image forming apparatuses is equipped with a plurality of exposure units which form a plurality of color images, and these exposure units are provided in the image forming apparatus at high positional accuracy. In particular, it is required that relative positional accuracy between the exposure units is high. If the positional accuracy between the exposure units is not satisfactory, displacement is caused between color images to cause doubling, resulting in deterioration of image quality. The positional relationship between exposure units needs to be maintained during the operation period of the image forming apparatus.
To satisfy the conditions about positions of the exposure units, a plurality of exposure units have been combined with UV adhesive agents, for example.
In the adjustment mechanism disclosed in the aforesaid patent publication, there are provided 6 adjustment means in total, because adjustment is made at two points for each of X, Y and Z directions. Therefore, the adjustment is complicated. Further, there has not been disclosed a concrete adjustment mechanism capable of attaining simple structure and high adjustment accuracy, in the prior art.
Further, in the fixing means to fix between exposure units by adhesive agents, a great many hours are needed for securing desired strength, which has been a problem in manufacture.
An object of the invention is to solve the aforesaid problems in conventional image forming apparatuses employing a light beam.
In order to attain the above-described objects, the structure of this invention has been made as follows:
An image forming apparatus, comprising:
a photoreceptor having an image carrying surface;
an exposing device to imagewise expose the image carrying surface to form a latent image; and
a developing device to develop the latent image to form a toner image on the image carrying surface;
the exposing device comprising:
a light source to emit a light beam;
a deflector to deflect the light beam so as to form a scanning line with the light beam on the image carrying surface;
a cylindrical lens provided between the deflector and the image carrying surface and to focus the light beam on the image carrying surface; and
an adjusting mechanism to adjust an inclination of the scanning line and to adjust variance in magnification of an image on the scanning line.
Further the above objects may be attained by the following structures.
(Structure 1)
An image forming apparatus having therein exposure units each being provided with a laser light source and a scanning optical system that deflects light coming from the light source and emits scanning light beam, the exposure units being supported on at least a first supporting point, a second supporting point and a third supporting point, wherein a first adjustment means that adjusts an inclination of the scanning light beam in the primary scanning direction is provided in a first supporting section where the first supporting point is provided, and the inclination in the primary scanning direction is adjusted only by adjustment of the first adjustment means.
(Structure 2)
An image forming apparatus having therein exposure units each being provided with a laser light source and a scanning optical system that deflects light coming from the light source and emits scanning light beam, the exposure units being supported on at least a first supporting point, a second supporting point and a third supporting point, wherein a second adjustment means that adjusts variation in magnification of the scanning light beam in the primary scanning direction is provided in a second supporting section where the second supporting point is provided, and the variation in magnification is adjusted only by adjustment of the second adjustment means.
(Structure 3)
The image forming apparatus according to Structure 1 above having therein exposure units each being provided with a laser light source and a scanning optical system that deflects light coming from the light source and emits scanning light beam, the exposure units being supported on at least a first supporting point, a second supporting point and a third supporting point, wherein a second adjustment means that adjusts variation in magnification of the scanning light beam in the primary scanning direction is provided in a second supporting section where the second supporting point is provided, and the variation in magnification is adjusted only by adjustment of the second adjustment means.
(Structure 4)
An image forming apparatus according to Structure 1 above having therein exposure units each being provided with a laser light source and a scanning optical system that deflects light coming from the light source and emits scanning light beam, the exposure units being supported on at least a first supporting point, a second supporting point and a third supporting point, wherein a first supporting section in which at least one supporting point among three supporting points is provided a spherical body bearing that supports the exposure unit rotatably in all directions.
(Structure 5)
The image forming apparatus according to Structure 1 or Structure 3 above, wherein the first supporting section is provided with a spherical body bearing that supports the exposure unit rotatably in all directions.
(Structure 6)
The image forming apparatus according to Structure 1 or Structure 3 above, wherein a movement of the first supporting point is conducted around a straight line passing through the other two supporting points which serves as the axis, and at least one of the other two supporting points can move in the direction that is mostly perpendicular to the movement direction of the first supporting section.
(Structure 7)
The image forming apparatus according to Structure 2, wherein the second supporting section is provided with a spherical body bearing that supports the exposure unit rotatably in all directions.
(Structure 8)
The image forming apparatus according to Structure 2 or Structure 3 above, wherein a movement of the second supporting point is a rotation around the first supporting point, and the second supporting section is provided with a slide which makes the exposure unit to move in the direction of a normal line for the direction of the aforesaid rotation.
(Structure 9)
The image forming apparatus according to either one of Structure 1-Structure 4 above, wherein the third supporting point is made to be a fixed point.
(Structure 10)
The image forming apparatus according to Structure 9, wherein the third supporting point is provided on the plane that mostly includes an optical axis of the scanning optical system and is mostly perpendicular to the scanning plane.
(Structure 11)
The image forming apparatus according to Structure 9 or Structure 10, wherein the first supporting point and the second supporting point are provided respectively on both end portions of an optical path formed by the scanning optical system.
(Structure 12)
The image forming apparatus according to either one of Structure 9-Structure 11 above, wherein the first supporting point and the second supporting point are provided respectively at positions which are mostly symmetrical about an optical axis of the scanning optical system.
(Structure 13)
The image forming apparatus according to Structure 4 above, wherein the spherical body bearing has a separation preventing member that prevents separation of the supporting spherical body.
(Structure 14)
The image forming apparatus according to Structure 13 above, wherein the separation preventing member is elastic.
(Structure 15)
The image forming apparatus according to Structure 13 or Structure 14 above, wherein the spherical body bearing supports the spherical body at three points thereon, and the separation preventing member makes the spherical body to be in pressure contact with the spherical body bearing by touching at least one point on the spherical body.
(Structure 16)
The image forming apparatus according to Structure 13 or Structure 14 above, wherein the spherical body bearing supports the spherical body in the shape of a circular ring, and the separation preventing member makes the spherical body to be in pressure contact with the spherical body bearing by touching at least one point on the spherical body.
(Structure 17)
The image forming apparatus according to either one of Structure 2-Structure 4 and Structure 9-Structure 16 above, wherein a distance keeping means that keeps a distance between the exposure unit and the second supporting section and an elastic member that presses the exposure unit against the second supporting section are provided in the vicinity of the second supporting section in which the second supporting point is provided.
(Structure 18)
The image forming apparatus according to either one of Structure 1-Structure 17, wherein the first supporting section is composed of a driving screw and an engagement plate that engages with the driving screw, and the first adjustment means is composed of the driving screw, the engagement plate and a driving source that drives the driving screw.
(Structure 19)
The image forming apparatus according to either one of Structure 1-Structure 18, wherein the second supporting section is composed of a driving screw and an engagement plate that engages with the driving screw, and the second adjustment means is composed of the driving screw, the engagement plate and a driving source that drives the driving screw.
(Structure 20)
The image forming apparatus according to Structure 18 or Structure 19, wherein the engagement plate stated above is composed of two sheets which engage with the driving screw respectively in two directions which are opposite to each other.
(Structure 21)
The image forming apparatus according to Structure 20, wherein the two engagement sheets are formed as protruded sections extended from one sheet of common base section.
(Structure 22)
The image forming apparatus according to Structure 20 or Structure 21, wherein the two engagement sheets engage with the driving screw at two positions which are deviated in terms of phase by approximately a half of a pitch of the driving screw each other.
(Structure 23)
The image forming apparatus according to either one of Structure 1-Structure 17, wherein the first supporting section is composed of a driving male screw and an engagement block which has a female screw that engages with the driving male screw and is fixed on the exposure unit, and the first adjustment means is composed of the driving male screw, the engagement block and a driving source that drives the driving screw.
(Structure 24)
The image forming apparatus according to either one of Structure 1-Structure 17, wherein the second supporting section is composed of a driving male screw and an engagement block which has a female screw that engages with the driving male screw and is fixed on the exposure unit, and the second adjustment means is composed of the driving male screw, the engagement block and a driving source that drives the driving screw.
(Structure 25)
The image forming apparatus according to Structure 23, wherein an engagement clearance between the driving male screw and the female screw is made to be 1.5 times the maximum position correction amount of the exposure unit or more, so that rotating operations of the driving male screw in the first supporting section may not be interrupted.
(Structure 26)
The image forming apparatus according to Structure 24, wherein an engagement clearance between the driving male screw and the female screw is made to be 1.5 times the maximum position correction amount of the exposure unit or more, so that rotating operations of the driving male screw in the second supporting section may not be interrupted.
(Structure 27)
The image forming apparatus according to either one of Structure 23-Structure 26, wherein the engagement block has two connecting members protruded in the direction perpendicular to a rotary axis of the driving male screw, and the engagement member is combined with the exposure unit by the connecting member.
(Structure 28)
The image forming apparatus according to either one of Structure 1-Structure 17, wherein the first supporting section is composed of a driving male screw, an engagement block that engages with the driving male screw and a driving source that drives the driving screw, and there are provided on the engagement block a hole through which the driving male screw enters and an engagement member that has a tip portion engaging with the driving male screw and engages with the engagement block through screw.
(Structure 29)
The image forming apparatus according to either one of Structure 1-Structure 17, wherein the second supporting section is composed of a driving male screw, an engagement block that engages with the driving male screw and a driving source that drives the driving screw, and there are provided on the engagement block a hole through which the driving male screw enters and an engagement member that has a tip portion engaging with the driving male screw and engages with the engagement block through screw.
(Structure 30)
The image forming apparatus according to Structure 1 or Structure 3, wherein a plurality of the exposure units are provided, and the first adjustment means stated above is provided on each of the plural exposure units.
(Structure 31)
The image forming apparatus according to Structure 1 or Structure 3, wherein a plurality of the exposure units are provided, and the second adjustment means stated above is provided on each of the plural exposure units.
(Structure 32)
The image forming apparatus according to Structure 3, wherein a plurality of the exposure units are provided, and the first adjustment means and the second adjustment means both stated above are provided on each of the plural exposure units.
(Structure 33)
The image forming apparatus according to Structure 1 or Structure 3, wherein the first adjustment mean has a driving source composed of a motor.
(Structure 34)
The image forming apparatus according to Structure 2 or Structure 3, wherein the second adjustment mean has a driving source composed of a motor.
(Structure 35)
The image forming apparatus according to Structure 1 or Structure 3, wherein the first adjustment mean has a driving source composed of a layered piezoelectric actuator.
(Structure 36)
The image forming apparatus according to Structure 2 or Structure 3, wherein the second adjustment mean has a driving source composed of a layered piezoelectric actuator.
(Structure 37)
An image forming apparatus having therein an exposure unit composed of a laser light source and a scanning optical system that deflects light coming from the laser light source and emits a scanning beam, a first supporting means that supports the exposure unit rotatably, a second supporting means that is in a form of a circular arc whose center is the first supporting means and supports the exposure unit movably along the circular arc, and a magnification adjustment means that adjusts variation of magnification in the primary scanning direction of the scanning optical system by the rotation around the first supporting means.
(Structure 38)
An image forming apparatus having therein an exposure unit composed of a laser light source and a scanning optical system that deflects light coming from the laser light source and emits a scanning beam, and an inclination adjustment means supporting the exposure unit, having a supporting shaft that is almost in parallel with an optical axis of the scanning optical system and adjusting an inclination in the primary scanning direction by rotating the exposure unit on the center of the supporting shaft.
(Structure 39)
An assembling method of an exposure unit for assembling the exposure unit for an image forming apparatus having therein a photoreceptor, a charging unit that charges the photoreceptor, a exposure unit that conducts scanning exposure on the photoreceptor with a light beam to form an electrostatic latent image and a developing unit that develops the electrostatic latent image formed on the photoreceptor, and having at least a plurality of the exposure units, wherein each of the exposure units is attached to a supporting means so that a position of the exposure unit is corrected, and then, the clearance formed between the plural supporting means is filled with melted resins so that the exposure units and a distance between the exposure units are fixed.
(Structure 40)
The assembling method of an exposure unit according to Structure 39, wherein each of the plural supporting means has a plane crossing in the direction in which the plural exposure units are separated each other, and mutual exfoliation is prevented by resistance of the resin itself filled in the clearance formed by the crossing planes.
(Structure 41)
The assembling method of an exposure unit according to Structure 39 or Structure 40, wherein the supporting means is made of resin, and a space between the supporting means is filled with resin that is the same in terms of a type as the resin of which the supporting means is made, and thereby the supporting means are combined each other through their clearances.
(Structure 42)
An assembling method of an exposure unit for assembling the exposure unit for an image forming apparatus having therein a charging unit that charges the photoreceptor, an exposure unit that conducts scanning exposure on the photoreceptor with a light beam and a plurality of image forming sections each having a developing unit that develops an electrostatic latent image formed on the photoreceptor which are arranged to face the photoreceptor, wherein each of the exposure units is attached to a supporting means so that a position of the exposure unit is corrected, and then, the clearance formed between the plural supporting means is filled with melted resins for fixing the position so that the exposure units and a distance between the exposure units are fixed.
(Structure 43)
The assembling method of an exposure unit according to Structure 42, wherein each of the plural supporting means has a plane crossing in the direction in which the plural exposure units are separated each other, and mutual exfoliation is prevented by resistance of the resin itself filled in the clearance formed by the crossing planes.
(Structure 44)
The assembling method of an exposure unit according to Structure 42 or Structure 43, wherein the supporting means is made of resin, and a space between the supporting means is filled with resin that is the same in terms of a type as the resin of which the supporting means is made, and thereby the supporting means are combined each other through their clearances.